The focus of this proposal is to investigate the active reorganization of intracortical connections in the developing visual cortex of ferrets following manipulations of correlated visual activity. I propose to study the effect of altering activity during the critical period of plasticity on the development and rearrangement of horizontal projections in layers II/III of the ferret visual cortex. Such changes are the first step in a cascade of events that lead to long-term alterations in cortical connections and function. Specifically, I will use two- photon imaging to image dynamically changing horizontal projections in vivo during normal development and after manipulations of activity by monocular lid suture or strabismus. I will relate these changes in anatomical architecture to functional changes in ocular dominance and orientation maps that will be obtained using optical imaging of intrinsic signals. [unreadable] [unreadable]